Part made of transparent material and headlight lens for vehicles

ABSTRACT

A part ( 1 ) made of transparent material that allows visible light waves to pass therethrough, said part comprising outer faces ( 11, 12 ) defining a solid body ( 10 ) made of transparent material, the part being characterized in that it further comprises light diffracting means ( 14 ) situated inside the solid body ( 10 ) at a distance from the outer faces ( 11, 12 ).

[0001] The present invention relates to a part made of transparentmaterial, and more particularly to a vehicle-headlight lens, which ismerely a part made of a transparent material that allows visible lightwaves to pass therethrough and that presents determined opticalcharacteristics. Vehicle-headlight lenses are usually designed to bemounted in front of a light source inside a headlight housing.

[0002] In order to modify the optical characteristics, in particular thediffraction characteristics, of a part made of transparent material orof a vehicle-headlight lens, or in order to impart opticalcharacteristics thereto, it is known to modify the surface state of saidpart or said lens so as to impart thereto an outer profile or patternfavoring diffraction of the light passing therethrough. This type ofsurface treatment is also used for purely esthetic purposes on partshaving purely decorative use. In other words, it is known to treat theouter surface of parts made of transparent material or of avehicle-headlight lens for a functional and/or decorative purpose.

[0003] To produce this special surface state, several techniques exist.A first technique consists in producing this surface state by molding,in particular while molding the part or the lens. To do this, the moldelements used for molding parts or lenses must define special imprintscapable of producing the desired surface state. However, that type ofmolding technique presents technical drawbacks, in particular a lack ofconstancy or of quality as a result of the mold elements aging, wearing,or else becoming clogged. It has been observed that the desired surfacestate varies over time, or each time the mold elements are cleaned. Withthat molding technique, it is therefore practically impossible to ensureconstant surface quality for parts made of transparent material or forvehicle-headlight lenses.

[0004] A second technique used to produce such surface states consistsin machining the part or the lens after it has been molded. Once again,it is difficult to ensure that surface state remains of constantquality. This results from the facts that abrasives are used to performthe machining, and that the quality of the surface states dependsdirectly on the grain size of the abrasives which vary not only overtime but also from one batch of abrasives to another. It has beenobserved that a very small difference in the grain size of the abrasivescreates a major difference in the desired surface states.

[0005] Furthermore, all surface-state treatments inevitably createirregularities or discontinuities in the surface of the part or of thelens, which favor the accumulation of dirt which significantly degradesthe optical or decorative qualities of the part or of the lens.

[0006] An object of the present invention is to remedy theabove-mentioned drawbacks of the prior art in general terms by defininga part made of transparent material, and more particularly by defining avehicle-headlight lens, in which optical qualities, and in particulardiffraction, are constant over time and from one part or from one lensto another. Furthermore, it must be possible to produce the part or thelens easily and at low cost.

[0007] To do this, the present invention proposes firstly a part made oftransparent material that allows visible light waves to passtherethrough, said part comprising outer faces defining a solid bodymade of transparent material, the part being characterized in that itfurther comprises light diffracting means situated inside the solid bodyat a distance from the outer faces. The part can be made of glass or ofa plastics material such as polycarbonate or methacrylate. Thediffracting means can advantageously be constituted by pointmicro-deteriorations of the solid body which can, for example, beproduced by a method of bombardment using laser radiation. When the partis made of glass, the point micro-deteriorations are in the form ofmicrosplinters as a result of the massive point supply of energy comingfrom the laser radiation. In the case of a part made of plasticsmaterial, the point micro-deteriorations are in the form of micromeltsas a result of the massive supply of energy coming from the laserradiation.

[0008] Naturally, the micro-deteriorations can be produced by usingtechniques other than the laser radiation technique.

[0009] By localizing the diffracting means inside the transparent part,out of contact with the outer surfaces thereof, parts can be producedhaving a perfectly smooth surface state such that they do not trap dirt.Furthermore, with such a laser bombardment method, a quality and adurable constancy of the diffracting means contained inside the part isensured.

[0010] The part can be a purely decorative part, which may optionally beilluminated, and for which the diffracting means are used to create adecorative or esthetic pattern that can be seen directly inside thetransparent part.

[0011] The transparent part can also be a functional part for which thediffracting means are used to deflect a portion of an incident lightray. For example, the diffracting means included within the part canserve to illuminate a zone that is otherwise quite dark.

[0012] The invention also provides a vehicle-headlight lens designed tobe mounted in front of a light source in a headlight housing, said lenscomprising outer faces defining a solid body made of transparentmaterial, the lens being characterized in that it further compriseslight-diffracting means situated inside the solid body at a distancefrom the outer faces. The lens can equally well be made of glass or ofplastics material such as polycarbonate or methacrylate. Thediffracting-means are advantageously constituted by pointmicro-deteriorations of the solid body of the lens, obtained, forexample, by a method of bombardment using laser radiation.

[0013] The invention finds an advantageous application in the case of avehicle-headlight lens for which optical and photometric properties areof greatest importance. Lenses are commonly used in vehicle headlights.The lens is used in association with a light source and a maskinterposed between the light source and the lens. The purpose of themask is to provide a cut-off in the emitted light beam. However, thecut-off made by the mask in the light beam is relatively sharp, and thelight beam presents a very low, indeed practically zero intensity abovesaid cut-off.

[0014] The fact that the light beam presents very low intensity abovethe cut-off can significantly hinder a driver who tries to see overheadinformation, e.g. on motorway signs.

[0015] Furthermore, regulations require a minimum light level in a“porch” zone, i.e. above the cut-off of the emitted light beam.

[0016] It is therefore necessary to illuminate the zone situated abovethe cut-off slightly, by reducing the contrast at the cut-off byspreading out the contrast gradient, so that the driver and the otherusers are not hindered.

[0017] Vehicle-headlight lenses which aim to achieve this object alreadyexist in the prior art. To do this, surface treatments are performedusing molding or machining techniques such as those described above withreference to the prior art. By way of example, document FR 2 770 617 canbe mentioned which describes a lens having a convex front face thatcomprises a series of curved surfaces that are capable of deflecting aportion of the light beam. The curved surfaces are formed together withthe lens itself by molding, and consequently suffer from theabove-mentioned drawbacks, namely: aging, wear, and clogging of the moldelements used to form the lens.

[0018] The present invention solves all those problems given that thediffracting means do not affect the outer surface of the lens, and giventhat they are also produced by a method enabling a constant quality tobe ensured therefor. The principle of the invention resides in the factthat the diffracting means are not formed outside the lens.

[0019] In an embodiment enabling the above-mentioned photometriccriteria to be achieved, the diffracting means extend in the solid bodyin a pattern favoring the diffraction of light towards a zone situatedabove a plane passing through the mid-plane of the lens when it is inplace in the headlight housing, i.e. in the zone situated above thecut-off.

[0020] In addition or in a variant, the diffracting means extend in thesolid body in a pattern forming a waveguide for an incident light. Thelens, in addition to being illuminated by the light source for thepurpose of illuminating the roadway, can be illuminated by an additionalsource emitting incident light which propagates in the waveguide formedby the pattern of the diffracting means. By way of example, theadditional light source can be illuminated while the main light sourceis turned off so as to impart an attractive esthetic effect to the lens,and more generally to vehicle headlights.

[0021] The lens is preferably an elliptic-type lens comprising a planerear face and a convex front face. The light source is thus placedperpendicularly to the rear face and the incident light is emittedparallel to the plane of the rear face.

[0022] The invention is described below in greater detail with referenceto the accompanying drawing showing, by way of non-limiting example, anembodiment of the invention:

[0023] In the figures:

[0024]FIG. 1 is a view in vertical cross-section through avehicle-headlight lens of the invention; and

[0025]FIG. 2 is a plan view of the FIG. 1 lens.

[0026] The embodiment used to illustrate the present invention is avehicle-headlight lens, but some other part made of transparent materialcould equally well have been used.

[0027] The vehicle-headlight lens shown in the drawing is anelliptic-type lens presenting a circular plane rear face 11 and a convexfront face 12 connected to the rear face 11 by a rim 13 which serves tofix the lens in a vehicle-headlight housing. The faces 11 and 12 definea solid body 10 which is entirely solid.

[0028] The solid body is preferably in a single piece and is notconstituted by strata or agglomerations.

[0029] The lens can be made of any transparent material that is able towithstand the heat emitted by the light source of the vehicle headlight.In particular, the lens can be made of glass or of a plastics materialsuch as polycarbonate or methacrylate.

[0030] If the lens is made of glass, it can be made from a single dropof molten glass. The resulting solid body is thus perfectly homogeneous.

[0031] In the invention, diffracting means for diffracting visible lightare formed inside the lens, i.e. in the solid body 10. The diffractingmeans 14 do not come into contact with the outer surfaces 11 and 12 ofthe lens 1. Nevertheless, a fraction of the diffracting means could alsobe situated on the outer faces 11 and 12. However, a portion of thediffracting means must be situated at a distance from the faces 11 and12. Indeed, it is preferable for the entire diffracting means to besituated at a distance from the faces 11 and 12.

[0032] The diffracting means are advantageously in the form of pointmicro-deteriorations of the sold body 10 of the lens. The pointmicro-deteriorations 14 can be produced by means of a forming methodusing laser radiation during which the lens is subjected to point laserradiation that can be displaced and that can be varied in intensity soas to form a pattern of point micro-deteriorations.

[0033] The micro-deteriorations are in various forms as a function ofthe constituent material of the lens. When the lens is made of glass,for example, the micro-deteriorations are in the form of microsplintersobtained by the massive concentration of energy supplied by the laserradiation. Alternatively, when the lens is made of plastics material,the point micro-deteriorations are in the form of micromelts.

[0034] The diffracting means can extend in the solid body in a patternenabling a functional and/or esthetic result to be obtained. The patternmade by the diffracting means can, for example, favor the diffraction ofthe light emitted by the light source of the vehicle headlight in such amanner as to illuminate even if only slightly an otherwise dark portion,e.g. the zone situated above the cut-off formed by the mask in aconventional vehicle headlight as explained above in relation to theprior art. The pattern of the diffracting means can, for example, directlight into the zone above the cut-off and thus soften the contrast atthe cut-off.

[0035] Furthermore, the diffracting means can also extend in the solidbody of the lens in a pattern forming a waveguide. By thus illuminatingthe lens sufficiently, it is possible to cause light to travel along thewaveguide in such a manner as to make the pattern formed by thediffracting means even more visible. The result is thus purely estheticand can be seen directly, but only when looking at the lens itself.

[0036] By way of example, it is possible to envisage a vehicle headlighthaving a housing that includes a main source of light designed to passthrough the lens so as to illuminate the roadway, and a secondary lightsource, e.g. a light-emitting diode (LED), used purely to illuminate thelens for esthetic purposes by using the diffracting pattern as awaveguide. The main source is situated in conventional manner behind theplane face 11 of the lens, while the secondary light source can beinstalled in the plane, or parallel to the plane formed by the planeface 11.

1/ A vehicle-headlight lens (1) designed to be mounted in front of alight source in a headlight housing, said lens (1) comprising outerfaces (11, 12) defining a solid body (10) made of transparent material,the lens being characterized in that it further comprises lightdiffracting means (14) situated inside the solid body (10) at a distancefrom the outer faces (11, 12). 2/ A lens according to claim 1, in whichthe transparent material is selected from glass and plastics materialssuch as polycarbonate or methacrylate. 3/ A lens according to claim 1 orclaim 2, in which the diffracting means are constituted by pointmicro-deteriorations (14) of the solid body (10). 4/ A lens according toany preceding claim, in which the diffracting means (14) extend in thesolid body (10) in a pattern favoring the diffraction of light towards azone situated above a plane passing through the mid plane of the lenswhen it is in place in the headlight housing. 5/ A lens according to anypreceding claim, in which the diffracting means (14) extend in the solidbody (10) in a pattern forming a waveguide for an incident light. 6/ Alens according to claims 4 and 5, in which the lens is an elliptic-typelens comprising a plane rear face (11) and a convex front face (12), thelight source being placed perpendicularly to the rear face (11) and theincident light being emitted parallel to the plane of the rear face(11). 7/ A method of forming diffracting means inside avehicle-headlight lens using laser radiation. 8/ A method according toclaim 7, in which the diffracting means are point micro-deteriorations,e.g. in the form of splinters, made in the bulk of a glass lens. 6.(Amended) A lens according to claim 4, in which the lens is anelliptic-type lens comprising a plane rear face (11) and a convex frontface (12), the light source being placed perpendicularly to the rearface (11) and the incident light being emitted parallel to the plane ofthe rear face (11).